1. Field of the Disclosure
This disclosure generally relates to a touch control device and, more particularly, to a touch control device and a determining method thereof, which determine a DPI curve according to contact areas of different objects.
2. Description of the Related Art
The conventional touch control device, such as a touch pad, generally has a touch surface and a processing unit. When a user moves his/her finger on the touch surface, the processing unit calculates a two-dimensional coordinate position of the finger corresponding to the touch surface and generates a displacement signal. Then, the processing unit outputs the displacement signal with a DPI (dots per inch) value to a host and correspondingly controls a cursor movement of the host.
FIG. 1A is a schematic diagram of a DPI curve, wherein the x-axis indicates a moving velocity (unit: inch per sec) of an object (e.g. the finger), and the y-axis indicates a cursor DPI corresponding to the object. The DPI curve represents a relationship between a moving velocity of a cursor and dots per inch. When a moving velocity of an object is slower, e.g. for editing an image, the cursor DPI becomes smaller so that a cursor corresponding to the object is accurately moved within a small region. And when the moving velocity is faster, e.g. for playing a computer game, the cursor DPI becomes larger so that the object controls the cursor to move for a long distance without moving too far. Therefore, an input device using a DPI curve provides a better user experience.
However, fingers of different users (e.g. adults and children) or even different fingers of the same user change a contact range with the touch surface. Thus, within the region of the touch pad, especially for a mini touch pad, a movable distance for a big object is obviously smaller compared to a movable distance for a small object. For example, referring to FIG. 1B, when an index finger 93 with a smaller contact range horizontally moves on a touch pad 91 from the left side to the right side thereof, a maximum travel distance X93 is obtained. When a thumb 95 with a larger contact range horizontally moves on the same touch pad (shown as 91′ herein) from the left side to the right side thereof, another maximum travel distance X95 is obtained. Obviously, since the contact range of the index finger 93 is smaller than that of the thumb 95, the maximum travel distance X93 is larger than the maximum travel distance X95. Accordingly, cursors C93 and C95 on display screens 81 and 81′ corresponding to the touch pads 91 and 91′ respectively move over distances X93′ and X95′, wherein X93′>X95′. Therefore, a shorter travel distance for a bigger object leads to the problem of a shorter travel distance for a cursor being moved.